1. Field of the Invention
This invention relates to tissue removal in a liquid environment and, more particularly, an improved surgical tip for cutting, aspirating and removing desired tissue by utilization of ultrasonic frequencies with minimal or reduced incidences of temperature increases along the axial length of the surgical tip.
2. Description of the Background Art
"Phacoemulsification" traditionally has referred to a method of treating cataracts of the lens of the eye whereby an ultrasonic device (consisting of a specific frequency generator, vacuum pump, handpiece, and cannula) is utilized to disintegrate the cataract, which is then aspirated and removed. A cataract is calcified tissue protein of the lens of the eye, its capsule, or both. An estimated 1.25 million people worldwide are blinded by cataracts each year. Traditionally, surgical removal of the lens is required. In the past, this procedure required an incision (post limbus scleral) large enough to permit extraction of the lens and implantation of an artificial lens. Now the procedure can be done through a very small (2-3 mm), suture-less incision of the clear cornea with less complications and much shorter healing times. Ultrasound energy generating sonic shockwaves, a wavefront or imploding microbubbles is used to fragment the cataract, which can then be aspirated and removed through the incision. This technique and method for extracting the lens cortex was originally described in U.S. Pat. No. 3,589,363 to Banko et al, the disclosure of which is incorporated herein by reference.
After extraction of the cataract, a replacement lens is then folded with forceps or an injector and inserted through the small incision. Over the last decade, phacoemulsification has become the generally accepted mode of cataract removal for the majority of ophthalmic surgeons.
Traditionally, phacoemulsification surgical instruments are used for the disintegration of diseased tissue of the eye, and in particular, the opaque hardened protein of the lens (cataract) of the eye. During phacoemulsification, high frequency ultrasound energy, which travels as sonic shock waves or a sonic "wavefront", ranging from approximately 5 to 70 kilohertz (kHz) is delivered to the eye via a hand held transducer that conveys the acoustic wavefront energy into the eye via a thin walled needle or cannula tip threaded to the handpiece. More specifically, ultrasound energy is generated by piezoelectric crystals or magnetostrictive elements which are aligned within a surgical handpiece and delivered through an energy transferring surgical tip.
In conjunction with the ultrasound energy, a surgical console includes a variable speed peristaltic pump thereby producing vacuum to the handpiece. Additionally, an irrigation fluid source is fluidly coupled to the phacoemulsification handpiece whereby aspiration fluid of a sterile solution is circulated around the surgical tip through a silicone sleeve that encompasses the outer diameter of the surgical tip.
During phacoemulsification, the ultrasonic probe or surgical tip is inserted into the eye through a small incision. The surgical tip has several functions: it vibrates at ultrasonic frequencies and it aspirates fluid and particles from the eye. The ultrasound energy vibrates microbubbles (somnulance) that implode and collapse which disintegrate the lens nucleus and the surgical tip aspirates the nuclear particles away. In order to maintain the stability or pressure within the eye, vasoelastic material (hyaluronic acid) is injected into the anterior chamber to maintain corneal stability. Irrigation fluid composed of a balanced salt solution is infused around the vibrating surgical tip via a sleeve to cool the tip and aid in flushing out the pulverized tissue matter.
The advantages of phacoemulsification stem from the surgeon's ability to operate with a smaller incision than is required for conventional cataract surgery. A smaller opening in the eye means better control over fluid pressure within the eye (chamber stability), a more rapid recovery of wound site incision, less surgery-induced astigmatism and almost immediate return of visual activity.
Recently, the general principles underlying phacoemulsification have begun to be applied to other surgical disciplines. For instance, Mentor O & O of Norwell, MA manufactures both cataract and liposuction phacoemulsification instrumentation. Liposuction is the removal of subcutaneous fat tissue with a blunt tip cannula introduced into the fatty area through a small incision. Suction is then applied and fat tissue removed. Liposuction is a form of plastic surgery intended to remove adipose tissue from localized areas of fat accumulation as on the hips, knees, buttocks, thighs, face, arms, or neck.
Despite the advantages of phacoemulsification over more invasive techniques of cataract treatment, the phacoemulsification procedure can result in complications such as non-vascular tissue burns and damage, endothelial cell loss which is critical for the endothelium pump mechanism feeding the cornea. More specifically, the inherent safety problems with phacoemulsification during microsurgery are 1) needle tip temperature spikes during occlusion which can lead to cornea tissue burns; 2) possible rupture of the eye lens capsular bag (posteriorly) due to needle proximity, ultrasound power or vacuum; 3) degradation, disruption or removal of structurally critical corneal endothelium cells; and 4) lens epithelial cells left behind in the capsular bag due to dispersion during phacoemulsification and attendant vacuuming of tissue during microsurgery. For instance, hard nuclei blockage of the surgical tip may occur during phacoemulsification that results in a stoppage of fluidics and accompanying spike in the tip temperature which may cause burning and damage to the cornea at the port site. Any burning or damage to the cornea can result in complications at the wound site.
Continuing efforts are being made to improve eye surgery methods and apparatus. Advances have been made to circumvent the problems associated with phacoemulsification both in the technical (i.e. "hardware") and technique aspect of the phacoemulsification surgery. Consider the large number of background patents that reference U.S. Pat. No. 3,589,363 to Banko et al. and teach cataract surgery techniques or apparatus.
In addition, apparatus for controlling the parameters of a phacoemulsification handpiece via the phaco machine are disclosed in another large number of patents. By way of example, note U.S. Pat. No. 5,591,127 to Barwick, Jr. et al.; U.S. Pat. No. 5,580,347 to Reimels and U.S. Pat. No. 5,520,633 to Costin. Manufacturers have developed micro-processing systems which permit a surgeon to operate without concern of occlusion by sensing the rise in vacuum and shutting down ultrasound power. Phaco machines allow the surgeon to preset or vary the aspiration rate, vacuum and ultrasound power.
For instance, the AMO.RTM. DIPLOMAX.TM., manufactured by Allergan, Inc. of Irvine, Calif. is designed to protect against corneal burns and permits the surgeon to program "Occulsion Mode Phaco.TM.", "Burst Mode Phaco.TM." and Autopulse Phaco.TM.". With Burst Mode Phaco.TM. a surgeon may deliver ultrasound via a single controlled burst or in multiple controlled bursts of power. Additionally, with the Autopulse Phaco.TM. a surgeon may adjust between pulse mode and continuous power based upon the type of sculpting and the density of the cataract. These systems are designed to react in microseconds to reduce or shut down power before damage can occur. However, these systems are often cost prohibitive.
Alternatively, surgeons are working on improved techniques that require less ultrasound power. For instance, some surgeons are working supercapsularly to protect the delicate structures within the bag or working within a smaller area of "operation" (i.e. pulling the divided pieces of lens to the center of the tip). Still further, some surgeons are attempting to utilize higher working vacuum in an effort to reduce the amount of ultrasound power required.
Lastly, numerous patents are drawn to phacoemulsification needles. By way of example, note U.S. Pat. No. D357,313; U.S. Pat. No. 5,213,569 to Davis; U.S. Pat. No. 4,689,040 to Thompson; U.S. Pat. No. 4,959,049 to Smirmaul; U.S. Pat. No. 5,653,724 to Imonti; U.S. Pat. No. 5,417,654 and U.S. Pat. No. 4,869,715 to Sherburne. Additionally, many "improved" needles are being advertised in the industry.
TurboSonics.RTM.MicroTip.TM. needle reduces tip size to 0.9 mm form the standard tip size of 1.1 mm. Due to its smaller inner diameter, surgeons must accommodate by utilizing a smaller incision and a higher vacuum power.
The Storz.RTM. MicroFlow.TM. needle utilizes straight longitudinal channels defined in the outer surface or diameter of the needle, thereby giving the MicroFlow.TM. needle the appearance of a "fluted Greek column" to permit fluid to enter the eye unimpeded through a 2.5 mm incision. These longitudinal grooves resemble linear extrusions and do not converge.
Additionally, Surgical Design manufactures phacoemulsification needles that incorporate square or diamond shaped distal tips. Utilizing these tips a surgeon may perform auto-crack phaco wherein the nucleus is cracked without chopping it with a second instrument.
Efforts to improve eye surgery apparatus and techniques continue. Accordingly, it is an object of this invention to provide an improvement which overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which is a significant contribution to the advancement of the art.
Another object of this invention is to utilize less phaco power thereby helping to preserve the corneal endothelium without reducing the efficiency of the phacoemulsification procedure.
It is a further object of this invention to provide a surgical tip which may be readily utilized with current commercially available phacoemulsification machines.
A further object of the present invention is to provide a surgical tip which is not effected by occlusion with lens material but works with the occlusion in a controlled manner.
A further object of the present invention is to provide a surgical tip which runs cooler thereby obviating the necessity to reduce the temperature of the sterile solution.
A further object of the present invention is to provide a surgical tip that virtually eliminates temperature spikes along the axial length of the surgical tip thereby protecting the non-vascular cornea tissue.
A further object of the present invention is to provide a surgical tip that facilities the ease of lens removal across the nucleus density spectrum.
A further object of the present invention is to provide a surgical tip having increased longevity.
A further object of the present invention is to provide an apparatus and method for producing micro-etching within a small bore lumen.
The foregoing has outlined some of the pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.